Telephone-exchange system



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w U U r @w I E S w a vi 0 E M M E KERR TELEPHONE EXCHANGE SYSTEM FiidMay 5, 1924 Oct. 19 1926.

n w% \w\ \Q tlhlil i so Mi-111K 1 1E313, O15 ROSEYBANK, NEW' YURI-i,ASSIGNOR T0 WESTERN ELECTRIC GOM- Pfirll'ii, 1N CORPORATED, OF Nlll/J"293.111,

ii, A CORLPOEATIGN 0? NEW YORK.

TELEPHONE-EXCHANGE SYSTEIVE.

Application filed May 5, 1924. Serial No. 711,040.

This invention relates to telephone exchange systems, and moreespecially to such systems as employ automatic switches in theestablishment and completion of talking connections.

In inulti-oflice telephone systems, it is the usual practice to providetwo wire trunks extending between the several exchanges. In effect,these interorlice trunks appear in contacts of so-called oliice selectorswitches at the calling oiiice, and. terminate in contacts of incomingselector switches at called ollices. When one of these trunk, is seizedfor the purpose of extending a calling line, provision is made forrendering it nonselectablc at the call ng oilice. ll hen connection hasbeen completed over such a ti. ml; to a called line at a distant office,provision is also made for allowing both the calling and calledsubscribers to control the release of the said trunk. The invention isparticularly applicable to such systems wherein the number ofinteror'lice incoming selector switches is less than the number of finalse lector switches and wherein the called subscriber has supervisionover the release of the incon'iing trunk.

Accordingly, it is the object of the invention to increase theefficiency of interoilice coninuuiication by allowing the release of anintero'll ice trunk to be controlled by a called subscriber, witi meansfor automatially and immediately releasing such trunk ilnlependently ofthe called subscriber, when the trunk is seized for the extension of asecond calling line prior to disconnection by the said allcd subscriber.

A feature of the invention relates to the means for rendering aninterollice trunk selectable for the purpose of con'ipleting a secondconversational connection thercover before the complete release of apreceding first conversational connection.

linotlnsr feature relates to an interoliice incoming selector trunkwhich has an automatic timed release feature combined with animn'iediate release feature, the latter being effective when the saidincoming selector is seized for the purpose of extending a secondcalling line prior to disconnection by the previously called line.

Other inherent features and advantages may be ascertained after aconsideration of the following detailed description of the operation ofa particular application of the invention.

ll hile for the purpose of description it has been chosen to illustratethe invention as applied to an automatic telephone system whereinswitches of the coordinate type are used, such as shown in the patent toC. L. Goodruln and J. N. Reynolds, No. 1,515,735 granted Nov. 18, 192%,it is understood that the invention in its broad aspects is not to belimited thereby. The invention may be as well applied to so called powerdrive systems and, in general, to any automatic telephone systen'iemploying markers and wherein the selectable condition of aninteroi'lice trunk is dependent upon disconnection by a called party.

The invention is described in connection with a telephone system such asdisclosed in the copending application of Warren W. Carpenter, SerialNo. 703,362, filed April 1, 1924.

Detailed desert 2050a.

Let it be assumed that the subscriber at station 101, whose telephoneline is located. in oliice 100, has initiated a call for the purpose oiconversing with the subscriber at station 121, whose line is located ina distant otlice. In the manner described in detail in the patent to B.l i illiams and. E. Gibson, No. 1,543,967 granted June 30, 1925, thecalling line 102 is extended by means of automatic switches in oliice100 to an idle interofl ce trunk such as 108, the latter beinginnnediately rendered non-selectable at the oliice selector switch toother calling lines. The seizure of trunk 108 causes the operation ofslow release relay 111 in through its left winding, upper armature andback contact of relay 128, upper left winding of repeating coil 121, tipconduc tor of the trunk, through apparatus in office 100, returning overthe ringside of the trunk, through the left lower winding of repeatingcoil 121, lower inner armature and back contact of relay 128 to groundthrough the right winding of relay 111. Relay 111 extends ground throughthe upper inner armature and back cont-act of relay 103, left armatureand contact of relay 111, left normal contacts of relay 123, senderselector start wire 122 to battery through the winda circuit traceablefrom battery.

ing of relay 11 The operation of relay 11 causes the actuation of senderselector switch to selectively ass ciate an idle incoming" sender aswith the interolfice trunk. For the manner in which relay 112 causes theoperation of switch 110, reference may be had to the patent to S. B.Williams and E. S. Gibson No. 1,543,967 granted June 30, 1025, andherein before referred to. As soon as an idle senoer has been connected,relay 103 operates, opening the circuit of relay 111 which releases. Thetip and ring conductors of the incoming trunk are new extended to thereceiving mechanism in the sender 12 and the sender at oiiiCe 100transmits series of characteristic impulses to cause the called linedesignation to be re-' corded on the registers of sender 1 0. Vi henrelay 103 operated, ground was re moved from the start wire 122, and anobvious circuit was closed for the holding relay 123. The operation ofclay 123 opens the sender selector starting circuit at a second point toprevent subsequent i'eoperation o relay 103, after completion ofconnection through switches 170 and 180. Relay 123 also connects groundthrough its right armature and contact, right normal contacts or" relay132 to the sleeve conductor'ot trunk 10-1. l i hen the designation ofthe called line has been recorded in sender 120, connee-tor is actuatedto connect the controlling marker to the sender. The marker 140 nowfunctions to control the selective operation of incoming switch andfinal switch so to connect trunk 10-1 with the called line 190. For adetailed description of the manner in which these latter operations areeh ected, reference may be had to the application of ll arren W.Carpenter, Serial No. 703,362, filed April 1, 1924-.

When the foregoing connection of trunk 10% and line has been completedthe sender selector switch 110, sender 120, connector 130, inarker 140,and the various connectors 150, 160, cte, are released and revert tocommon use. The release of the sender selector switch 110 causes therelease of relay 103, thus completing; connection of the interol'licetrunk 1053 with the left windings of repeatingcoil 121., causingreoperation of relay 111. Relay 123 being slow to release does notretract its arinatures during: the interval between the release of relay103 and the operation of relay 111. As soon as relay 111 reoperates, itprovides a locking circuit for relay 123. This circuit may be tracedfrom battery through the winding of relay 123, lower inner arn'iatureand contact of relay 103, left outer armature and contact of relay 129,left armature and front contact of relay 123, left armature and contactof relay 111 "to ground at the upper inner armature and contact of relay103. The reopv 10. w A. I aeiay rat, loner ()llti c.iniatuie and coweration of relay 111 also extends this grounu over conductor 1%,conductor 1 armature and contact of relay 120, lower inner armature andcontact of relay 125 to be tery through the winding oi ringing controlrelay 12 1. This ground is also erlcndcd by 1116:1118 of conductor 15throi i the windi oi? relay which does not ope 'ate at this time sinceits vinding is shunted. 'llhe operation of relay 12lconiiects currentfrom he ringing; source 153 through the winding ot relay 120, rightarn'iature and contact ol" :tll of relay 125, ring conductor of trunk104-, contacts oi switch 1T0, condactor of trunk 105, contacts or switch180 through 1 me 1": 'nig apparatus at tne caller-i sub- SCIllJQlI'.station and return. thence through contacts or switch 180, tip conductoroi trunk 105, contacts of switch 170, tip cononctor of trunk 104-, upperouter armature and contact or' relay 1.25, to A ground at the leftarmature of rela ll hen the subscriber at station 121 removes thereceiver from the sw'tchhoolr the resii-i ance of the above tra edcircuit throragn of relay 126 is reduced, and this relay operates. Relay126 at arn'iarn 'e and contact removes the shunt from the winding ofrelay 125 which now operates to h grounded conductor 154;, thusextending the tip and ring coi'iduetors of tr right windings oirepeating CO1 crating sup visory relay 12. -4 closes an bviousoperatingg' circuit to 128 which reverses the current in dnctors at tWhen the conversation to; the calling subscriber replaccs receiver uponthe enritchhook, clay 111 release: The release of relay 111 reniovesground from the conductor 15-1, but it the called subscriber has notll'iQEtIlWliilG replaced the receiver, relay 125 reinains operated in acircuit traceable from battery through its inding, conductor 15%, windinof rela y 120, left normal contacts of relay r82 to ground at the lowerarmature and contact of relay 2S. Relay 120 operates in this circuit andat its right inner armature and contact maintains a busy potential onthe sleeve conductor of trunk 10 1-. hen interrupter 161 clos lowercontact, ground is connected through the right outer arn'iature andcontact of re lay 129, left normal contacts of relay 131 to batterytl'irougrh the winding 01 the same. Relay 131 looks through its windingand loclr'ng contact to ground at the right inner arn'iature of relay129. Should the called. subscriber n'iaintain the receiver oil theswitchhoolr indefinitely, the circuits are so arranged that alter apredetermined inter al cg'ulated by the time of closure of the upper andLALU

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contact of interrupter 161, the trunk 104, switches 170, 180 andassociated apparatus are automatically released. lVhen thereforeinterrupter 161 closes its upper contac assuming that the calledsubscriber still ha the receiver off the switchhook, ground is connectedthrough the right armature and contact of relay 131 to battery throughthe winding of release relay 132. Relay 132 locks through its winding,left armature and front contact to ground at the lower armature andcontact of relay 128. Relay 132 at its left normal contacts opens thecircuit for relays 129 and 125. These latter relays new release. Relay125 severs the tip .and ring conductors of the incoming selector trunk,and relay 129 removes holding ground from the sleeve conductor. In themanner described in the above mentioned application of Warren Carpenter,Serial No. 708,362, filed April 1, 1924, removal of ground from thesleeve conductor of trunk 10 1 causes the release of the connectionthrough switches 170 and 180. This severance of the connection causesthe release of relay 127 which in turn causes the release of relay 128.The connection has thus been completely restored to normal following theclosure of the upper contact of interrupter 161. From the foregoingdescription, it will be seen that provision is made for automaticallyreleas ing, after a definite interval an interotlice incoming selectorwhen the called party fails to disconnect following the termination ofconversation.

Assume that a connection has been completed by means of trunk 108 tocalled line 190, and after the termination of conversation, the party atstation 121 fails to replace the receiver upon the switchhook within thepredetermined time. Under these conditions, should the trunk 198 beagain seized by a selector switch in the ollice 100 during theii'iterval between disconnection of a previous calling party and theclosure of the upper contact of interrupter 161.the incoming sclectorwill be immediately disconnected from the previous called line andrendered available in extension of the second calling line.

In this case, relays 1.11, 125, 127, 128. and 129 are operated. hentherefore trunk 198 is seized by an office selector at this time, relay111 will operate as hereinbefore described. The operation of relay 111closes a circuit for release relay 132 which may be traced from batterythrough the winding thereof, left inner armature and contact of relay129, left armature and contact of relay 111 to ground at the upper innerarmature and contact of relay 103. The operation of relay 132 bringsabout the successive release of relays 125, 129, 127, 128 and switches170, as before described. Thus, the incoming selector is immediatelyrendered selectable by a second calling line, even though the previouscalled party has failed to replace the receiver within the specifiedtime.

What is claimed is:

1. In a telephone exchange system, a calling oliice, a called oilice,lines in said calling oliice, lines in said called OlllCG, a two-wiretrunk for completing connections between lines in said calling officeand lines in said called oltice, means at said called ollicc formaintaining said trunk in engagement with a called line after said trunkhas been disengaged from the calling line. and means under control ofsaid calling oliice for disengaging said trunk from said called lineafter said trunk has been disengaged from said calling line.

2. In a telephone exchange system, a calling office, a called office,lines in said calling otlice, lines in said called. oflice, a two-wiretrunk for completing connections between lines in said calling otliceand lines in said called office, means at said called office formaintaining said trunk in engagement with '1 called line after saidtrunk has been disengaged from the calling line, and means located insaid called ofiice under control of said calling oliice for disengagingsaid trunk from said called line after said trunk has been dis-engagedfrom said calling line.

3. In a telephone exchange system, calling lines, called lines, atwo-wire trunk extend ing between said calling and said called lines,means for completing a connection from one of said calling lines oversaid trunk to a particular one of said called lines, means under controlof said called line for naintaining said called line in engagement withsaid trunk, and means responsive to the extension of a second callingline to said trunk prior to disconnection ofsaid called line therefromto cause a forced disconnection of said called line to immediately allowsaid trunk to be used in completing the connec tion of said secondcalling line to another or the same particular called line.

4-. In a telephone exchange system, calling lines, called lines, aselector trunk for extending one of said calling lines to a particularone of said called lines, means for preventing said selector trunk fromcompleting other talking connections while either said calling or saidcalled line is connected thereto, and means effective upon disconnectionof said one of the calling lines and responsive to the extension ofanother of said calling lines prior to disconnection of said called linefor causing a forced disconncction of said called line to thereby allowsaid trunk to extend said other calling line.

5; In a telephone exchange system, calling lines, called lines, aselector trunk for extending one of said calling lines to a particularone of said called lines, means for preventing said selector trunk fromcompleting other talking connections while either said calling or saidcalled line is connected thereto, means for forcing a release of saidselector trunk when said calling line disconnects prior to disconnectionby said called line, a timing ar nngementfor timing the actuation orsaid forcing means, and means ellective upon a second seizure of saidselector trunk prior to disconnection by said called lin-e torrendering; said timing arrangement ineffective and for causing animmediate torced release of said selector trunk.

(3. In a telephone exchange system, calling lines, called lines, aselector switch for extending; one of said calling lines to a particularone oi said called lines, means for preventing said selector switch"from releasing while either said calling or said called line isconnected thereto, means for forcing; a release of said selector switchwhen said calling line disconnects prior to disconnection by said calledline, a timing arrangement for timing the actuation of said forcinn;means, and means ell'ective upon a second seizure of said selectorswitch prior to disconnection by said called line for rendering;- stiming arrangement ineffective and for causing an immediate forcedrelease of said selector switch.

'4". In a telephone exchange system, calling lines, called lines, atwo-wire trunk for extending one of said calling lines to a particularone of said called lines, means for preventing}; said trunk fromcon'ipleting other talking); connections while either said calling orsaid called line is connected thereto, means for forcing a release ofsaid trunk when said. calling line disconnects prior to disconnection bysaid called line, a a tin'iine; arrangement for timing the acluation ofsaid forcing means, and means ellective upon a second seizure of saidtrunk prior to disconnection by said called line for rendering saidtiming arrangement ineli'ective and for causing an immediate. forcedrelease of said trunk.

S. in a telephone exchange system, a calling line, a called line, aselector trunk for extending said calling line to said called line, atiming arrangement associable with said trunk, means responsive todisconnection by said calling line prior to disconnectien by said calledline for rendering said timing arrangen'ient etlective to cause a'forceddisconnection oi said called line from said selector trunk, and meansell'ecti-ve upon a second seizure of said selector trunk prior todisconnection by said called line for causing an in'nnediate iorceddisconnection of said valled line from said selector trunk.

9. In a telephone exchange system, a calling line, a called lic, aselectorswitch for extending said callingline to said called line, atiming arrangement associable with said switch, means responsive todisconnection by said calling line prior to disconnection by said calledline for rendering said timing arrangement eiiective to cause a forceddisconnection of called line from said selector switch, and meanscfl'ective upon a second seizure of said selector switch prior todisconnection by said called line for causing an immediate forceddisconnection of said called line from said selector switch.

10.111 a telephone exchange system, a calling line, a c lled line, aselector trunk for completing connections between said calling; line andsaid called lines, a timing arrangement associable with said selectortrunk, means responsive to disconnection by said calling line prior todisconnection by said called line for rendering said timing arrangementelli'ective to cause a forced release of said selector trunk, and meanseffective when said selector trunl'; is seized second time prior todisconnection by said called line for causing an immediate release ofsaid selector trunk.

ll. In a telephone exchange system, a calling line, a called line, atwo-wire trunk for conmleting connections between said calling line andsaid called lines, a timing arrangen'ient associated with said two-wiretrunk, means responsive to disconnection by said calling line prior toisconnection by said called line for rendering said timingarrangementetl'ective to cause a forced release of said two-wire trunk, and meansof tective when said two-wire trunk is seized a second time prior todisconnection by said called line for causing an immediate release ofsaid twowire trunk.

In witness whereof, I hereunto subscribe my name this 29th day of April,A. D. 19%.

MARK B. KERR.

